2019-10-12_The_Economist_

82 Science & technology The EconomistOctober 12th 2019

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world’s computers and phones. In the

1980s he was working at the Asahi Kasei

Corporation, in Japan, at a moment when

electronics companies were becoming in-

creasingly interested in lightweight batter-

ies that could power new electronic de-

vices such as video cameras and cordless

telephones. Dr Yoshino was happy with Dr

Goodenough’s cathode, but felt that the an-

ode needed redesigning.

Instead of lithium, he tried various car-

bon-based materials that might hold lithi-

um ions. He found success with petroleum

coke, a by-product of the fossil-fuel indus-

try. This, he discovered, could hold such

ions in abundance. His design was not only

safer than using a pure lithium anode (lith-

ium has a distressing tendency to catch

fire), but longer lasting, too. In Dr Yoshino’s

version of the battery, both anode and cath-

ode have a long life because they are not

damaged by chemical reactions as the bat-

tery is used or recharged. By 1991, the first

lithium-ion battery based on Dr Yoshino’s

design had been commercialised by Sony,

an electronics company.

Speaking at a press conference shortly

after being awarded the prize, Dr Yoshino

said he had pursued his research in the

1980s purely to satisfy his own curiosity,

without much thought as to whether or not

his inventions would one day be useful.

Given the lithium-ion battery’s subsequent

(and continuing) importance, Dr Yoshino’s

curiosity ended up fulfilling Nobel’s will to

the letter.

Cosmic thoughts

The physics prize was split two ways, but

both halves went for discoveries beyond

Earth. One was for a finding that is, by as-

tronomical standards, quite close by—a

planet going around a star a mere 50 light-

years distant. The other was for an over-

view of the entire universe.

In October 1995 Michel Mayor and Di-

dier Queloz, a pair of astronomers then

working at the University of Geneva, pre-

sented a paper at a scientific conference in

Florence. A few months earlier, they had

discovered a planet beyond the solar sys-

tem. It was a gaseous ball twice the size of

Jupiter and was going around a star called

51 Pegasi, at a distance of about 8m kilo-

metres—a twentieth of the distance from

Earth to the sun. As a consequence of this

proximityitorbited 51 Pegasi once every

fourterrestrial days and had a surface tem-

peratureinexcess of 1,000°C. The discov-

erywasapuzzle for astronomers. Until

thentheyhad thought that such large, Jupi-

ter-like planets could form only far away

from their host stars.

That discovery of 51 Pegasi b, as this

planet is now known, launched the field of

exoplanet astronomy. To date, astrono-

mers have found almost 4,000 other such

planets—and the wide variety of sizes, or-

bits and compositions of these objects con-

tinues to surprise researchers, who have

yet to come up with a comprehensive phys-

ical theory of how planetary systems form.

Since planets do not shine by them-

selves, astronomers needed to develop

special methods to find them. The one Dr

Mayor and Dr Queloz used relies on a phe-

nomenon called the Doppler effect. As a

planet orbits its star, that star will also

move slightly, as it is pulled around by the

gravity of the planet (see diagram 2). This

will cause the frequency of the starlight ar-

riving at Earth to oscillate (that is, the star

will change colour slightly) in the same

way that the frequency of an ambulance si-

ren shifts as the vehicle passes by. Nowa-

days a second approach, which measures

the dip in starlight as a planet passes across

its disc, is more common. But the Doppler-

shift method, as employed by Dr Mayor and

Dr Queloz, is still used as well.

The half-prize for the overview of the

universe went to James Peebles of Prince-

ton University, who has spent decades de-

veloping a theoretical framework to de-

scribe how the cosmos evolved from the

Big Bang 13.7bn years ago to the state it finds

itself in today. According to Sweden’s Royal

Academy of Science, which awards the

physics prize, Dr Peebles was the person

who, in the 1960s, shifted cosmology from

speculation to a rigorous discipline.

Until the first decades of the 20th cen-

tury, astronomers had assumed the uni-

verse to be stationary and eternal. This was

shown to be incorrect in the 1920s, with the

discovery that all galaxies are moving away

from each other. In other words, the uni-

verse is expanding. Rewind the clock and

this means that, at the start of time, now

called the Big Bang, the universe would

have been incredibly small, hot and dense.

Around 400,000 years after the Big

Bang it had expanded and cooled enough

for light to travel through space unimped-

ed. Astronomers can detect the glow of that

first light today but, because its wavelength

has been stretched by 13bn years of the ex-

pansion of space, it manifests itself not as

light but as a glow of microwave radiation

that fills the entire sky. This cosmic micro-

wave background was discovered, by acci-

dent, in 1964 by radio astronomers, who

used earlier theoretical work by Dr Peebles

to explain their discovery. Dr Peebles also

showed that tiny fluctuations in the tem-

perature of the microwave background

were crucial to understanding how matter

would later clump together to form galax-

ies and galaxy clusters.

Since the early 1990s, space-based ob-

servatories have built up increasingly pre-

cise portraits of the cosmic microwave

background and, true to Dr Peebles’s pre-

dictions, these show that temperature va-

riations of just one hundred-thousandth of

a degree map onto the observed distribu-

tion of matter and energy in the universe.

Rewarding cosmic shifts in under-

standing might seem to be a normal day’s

work for those who give out the Nobel

prizes. But Martin Rees, Britain’s Astrono-

mer Royal, sees something new in this

year’s awards in physics. The award to Dr

Peebles, he says, will be welcomed by phys-

icists as recognition of a lifetime of sus-

tained contributions and insights by an ac-

knowledged intellectual leader, rather

than a one-off achievement.

Such lifetime-achievement awards are

more usually associated with the Oscars

than the Nobels. But that is not inappropri-

ate. In many ways the Nobel prizes are a

Swedish version of the Oscars—with seri-

ousness substituted for superfice, sub-

stance for style, and genuine modesty

among the winners for the false sort.

The oxygen of publicity

Those qualities were certainly to the fore in

the award of the prize for physiology or

medicine. This shone a spotlight onto work

that, though of crucial importance in un-

derstanding how human bodies work, is—

unlike batteries, exoplanets and matters

A better battery^1

Source: NobelFoundation

Workingsofa lithium-ioncell

Electrolyte

Carbon

anode

Cobalt

oxide

cathode

Lithium-permeable barrier

Lithium ions

Electrons

–+

A swiftly revolving planet

Source:NobelFoundation

DetectionofexoplanetsbyDopplershift

2

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LP

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RA

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TA

IT

NO

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Orbit away from Earth

Star’s light shifts

to red spectrum

Star’s light shifts

to blue spectrum

Orbit towards Earth

View from Earth

EXOPLANET

EXOPLANET

Lightwaves

compressed

Lightwaves

stretched

PARENT

STAR